Global warming appeared during the last decade as a serious environmental issue, and it has been the subject to much debate. Global warming is the warming of the Earth by greenhouse gases emitted into the atmosphere either naturally or by mankind. These gases get trapped into the atmosphere and surround the Earth like a warm blanket ("Global warming 8"). These gases are necessary and are responsible for holding Earth's temperatures and climate patterns in a constant and normal range. However, these gases are steadily increasing. The 20th century's 10 warmest years have all occurred in the last 15 years ("Climate 2"). There are many different theories surrounding the causes of global warming, but the two main causes are the result of people and human activity, and a natural warming of the Earth.

One main cause of global warming is mankind. What has changed in the last few hundred years is...